An information device for informing a warning to a driver of a vehicle is disclosed in JP-A-H11-14379. The device informs the warning with using an image or a sound when a vehicle speed exceeds an optimum speed. The optimum speed for entering into the curve is calculated based on curvature information of the curve stored in memory medium.
Another information device including an air pressure sensor, a determination unit and a navigation system is disclosed in JP-A-2005-119533. The air pressure sensor detects air pressure in a tire, which is mounted in a vehicle. The determination unit determines whether the tire pressure detected by the sensor is in a predetermined range. The navigation system searches a planning driving route from a current position to a destination. Based on the planning driving route, the device preliminarily estimates road conditions such a highway and a curve. The device informs a driver of the vehicle to pump the tire if necessary.
However, the devices disclosed in the above prior art inform the warning without considering a type of the tire. Accordingly, even when the tire has excellent tire grip performance, the device may inform the warning, which is the same as the warning in a case where the tire has low tire grip performance. Thus, the device does not inform the warning according to the type of the tire mounted in the vehicle.